The subject of the present invention is a device for providing holographic movies or motion pictures and so obtaining for spectators the effect of relief.
It is known that if it is desired to record by means of holography objects having dimensions greater than 1 m, the amount of light diffused by this object and striking the sensitive surface is small. To form a hologram, which receives both this diffused light and a coherent reference wave, exposure times greater than a second must be used with lasers having a power of the order of a watt. This is due to the low sensitivity of the photographic support media of high resolution required for holographic recording. It is then not possible to record the 20 images per second required for the projection of movies.
It is further known, particularly from the article by J. P. Huignard and A. Marrakchi published in "Optics Communications", volume 38 (1981), page 249, to amplify a wavefront in photorefractive crystals such as Bi.sub.12 SiO.sub.20 (B.S.O.), by mixing two waves.
The present invention, using optical amplification, allows a hologram to be obtained requiring an exposure time compatible with the cinema.